Dose-response Effects of Dietary Nitrate on Running Time-to-exhaustion and Neuromuscular Fatigue: a Randomized Crossover Exploratory Pilot Study

Background: Dietary nitrate is a natural compound found in vegetables such as beetroot and leafy greens. Previous research suggests that consuming nitrate before exercise may improve endurance and physical performance. However, it is still unclear whether higher doses provide greater benefits, particularly in recreationally trained individuals. Purpose: This study aimed to investigate whether different doses of dietary nitrate taken before exercise influence endurance performance and muscle fatigue during a running test in recreationally trained men. Methods: This randomized, double-blind, placebo-controlled crossover pilot study compared the effects of a placebo and three different doses of dietary nitrate consumed before exercise. On separate occasions, participants completed the same treadmill running test to exhaustion after ingesting the assigned supplement. Measures of muscle performance, blood lactate concentration, and perceived exertion were collected before and after exercise to evaluate the effects of dietary nitrate supplementation.

Inclusion Criteria: * Male adults aged 18 to 40 years. * Recreationally trained, performing endurance or combined endurance/resistance exercise at least 3 times per week for the previous 6 months. * Maximal oxygen uptake (VO₂max) consistent with recreational training status. * Able to perform maximal treadmill running exercise. * Willing and able to comply with all study procedures. * Provided written informed consent before participation Exclusion Criteria: * Current smoking or use of nicotine products. * History of cardiovascular, pulmonary, metabolic, neurological, or musculoskeletal disorders that could affect exercise performance or participant safety. * Current use of medications or dietary supplements known to influence nitric oxide metabolism or exercise performance (e.g., nitrate supplements, phosphodiesterase-5 inhibitors, antibacterial mouthwash). * Allergy or intolerance to beetroot or any component of the study supplements. * Following a vegetarian or vegan diet, or habitually consuming a high-nitrate diet. * Consumption of alcohol, caffeine, or strenuous physical exercise within the period restricted by the study protocol before each experimental visit. * Failure to comply with pre-test dietary or behavioral instructions. Participation in another clinical trial within the previous 30 days. * Any condition that, in the opinion of the investigators, could interfere with study participation or interpretation of the results.